Various embodiments relate to a fluid transfer device, a flow cell, a sample separation device and a method of operating the same.
In high-performance liquid chromatography (HPLC), a fluid (mobile phase) is typically moved through a stationary phase (for example, a chromatographic separation column) at a precisely controlled flow rate (for example, in the region of microliters or milliliters per minute) and at a high pressure (for example, 20 bar to 1000 bar and beyond, currently up to 2000 bar), at which the compressibility of the fluid is perceptible, in order to separate from one another individual components of a sample liquid introduced into the mobile phase. Detection of the separated fractions of the sample then takes place in a flow cell of a liquid chromatography device. For this purpose, the fluid sample is conveyed from a capillary downstream of the chromatographic separation column into a container of the flow cell. While the fluid sample is passing through the flow cell, a fluorescence measurement of the fluid sample can be performed, with which the individual fractions of the fluid sample can be identified or quantified.
An example of such an HPLC system is described by EP 0,309,596 B1 of the same applicant, Agilent Technologies, Inc., the entire contents of which are hereby incorporated by reference.
During the transfer from the capillary downstream of the chromatographic separation column to the flow cell, the fluid is transferred from the capillary, which has a small cross-sectional area, into the flow cell container, which has a much larger cross-sectional area. Due to the sudden widening of the diameter of the fluid line, undesired effects often occur at this fluid interface, such as turbulence of the fluid sample, the occurrence of a turbulent flow or the formation of a dead volume through which the fluid sample does not flow. Both may cause artifacts, and thus reduce detection accuracy of the liquid chromatography device. Similar and other problems may also arise with other applications, where a fluid is transferred from a fluid line having a smaller diameter into a fluid line having a larger diameter.
In fluid handling devices, an artifact-free and dead-volume-free transfer of a fluid between fluid lines of differing cross-sectional areas is thus still difficult.